The Operational Core of the Penn/PGC CRC on Psychiatric/Medical Comorbidity in the Aged is designed to conduct epidemiological surveys on the patient populations of the Center and to serve its Laboratories through consultation to investigators and assessment, diagnosis, recruitment, and tracking of subjects. The Core is directed by G. Gottlieb and consists of three services: the Assessment, Recruitment and Tracking (ART) Service, the Psychiatric Diagnostic Service (PDS) , and the Geriatric Medicine Service. The ART Service is a resource for consultation on issues of assessment that also has responsibilities for screening populations, identifying potential research subjects, and instituting the process of their recruitment into research studies, as well as for that component of the Core's data acquisition that can be conducted by research assistants without formal clinical training. The PDS conducts standardized psychiatric diagnostic assessments, both to validate measures used by the ART Service and to ensure that subjects entered into the research of the laboratories are well-characterized; it also serves as a consultative resource on clinical geriatric psychiatry and neuropsychology. The GMS works together with the ART Service to establish and validate standardized methods for using medical records, clinician reports, and subject (or proxy) report to characterize the medical status of research subjects both in terms of summary measures of "medical burden" and disease-specific measures.